Surgical left atrial appendage occlusion (LAAO) is associated with a reduction of thromboembolism and all-cause mortality among older atrial fibrillation (AF) patients undergoing cardiac surgery, according to an observational study in the USA.

The results were presented in a session on late breaking clinical trials at the 2017 scientific session of the American College of Cardiology (ACC; 17–19 March, Washington, DC, USA).

Daniel Friedman, study’s lead author and presenter of the findings, said: “While our study was not a randomised trial, it does demonstrate strong support for the benefits of closing the left atrial appendage at the time of cardiac surgery in patients with atrial fibrillation.” Friedman is a fellow in cardiovascular diseases at Duke University Hospital and a research fellow at the Duke Clinical Research Institute, where his focus has been on sudden cardiac death, pacing in heart failure, and non-pharmacologic approaches to the treatment of atrial fibrillation.

The left atrial appendage (LAA) is implicated as the site of thrombus formation in 90% of thromboembolic events among patients with non-rheumatic AF. Although systemic oral anticoagulation with either warfarin or a direct oral anticoagulant significantly reduces the risk of thromboembolic stroke, as few as half of all eligible patients take the medications. The LAA can be surgically occluded at the time of cardiac surgery, although there are limited data supporting the effectiveness of this approach.

This study was a large comparative effectiveness analysis of surgical LAAO versus no surgical LAAO in a contemporary, nationally representative cohort of 10,524 Medicare beneficiaries (recorded in The Society of Thoracic Surgeons Adult Cardiac Surgery Database) with AF who underwent cardiac surgery in the United States, of which 3,892 (37%) patients underwent LAAO. The researchers performed inverse probability weighted (IPW) analyses to estimate the risk adjusted association between surgical LAAO and no surgical LAAO and outcomes at the time of cardiac surgery (35% coronary artery bypass graft [CABG], 35% aortic procedure ± CABG, 30% mitral procedure ± CABG). The primary outcome was rehospitalisation for thromboembolism at one year, with secondary outcomes haemorrhagic stroke, all-cause mortality, and a composite endpoint consisting of all-cause mortality, thromboembolism, and haemorrhagic stroke.

Surgical LAAO was associated with a 38% reduction in thromboembolism, a 15% reduction in all-cause mortality, and a reduction in the composite endpoint, but not with a reduction in haemorrhagic stroke. In IPW analyses stratified by discharge anticoagulation status, with adjustment for concomitant surgical AF ablation, LAAO was associated with less thromboembolism among those discharged without anticoagulants. There was no difference in thromboembolism rates for those who were taking anticoagulants at discharge. Friedman suggested that there is potential for future investigations to determine whether left atrial appendage occlusion is effective enough to allow patients to safely stop taking anticoagulants, as well as studies that compare different techniques used to close the left atrial appendage.

The study is limited by the fact that it is an observational analysis, with endpoints determined by claims data, and the discharge anticoagulation status may not be predictive of long-term anticoagulation strategy. In addition, it had a retrospective, non-randomised design. The researchers have advocated that the findings be confirmed in adequately powered trials, and said that further randomised data are needed.

Friedman believed this study suggests it is reasonable to routinely consider use of surgical LAAO in patients with AF undergoing cardiac surgery. “Intuitively, surgical left atrial appendage occlusion should work. However, there have been concerns that incomplete occlusion actually could lead to increased risk for thromboembolism because it could result in small communications between the appendage and the left atrium. The fact that we saw such a dramatic association between the procedure and a reduction in thromboembolism was reassuring that—at least in a more contemporary cohort of patients—left atrial appendage occlusion is able to be done in a much more effective way than initial reports had suggested may be the case.”

The study was funded by grants from the Burroughs Wellcome Fund and the US Food and Drug Administration. Friedman receives funding from the National Institutes of Health T 32 training grant HL069749.